The invention relates to tennis teaching aids.
The game of tennis requires a player to make a variety of strokes with the racquet. Some of the most effective strokes are topspin strokes but many players find difficulty in hitting strokes with topspin. Topspin strokes require the racquet, at the moment the ball is hit, to be travelling not only in the direction the ball is desired to travel off the racquet but also to be travelling at an angle to that path inclined towards the court surface so that the ball leaves the racquet spinning in the same direction that it is moving. This causes the ball to dip towards the court surface more quickly that would otherwise be the case and so gives the player a greater margin of error as well as producing a shot that is more difficult to return.
In order to impart such topspin, therefore, a player needs to be capable of maintaining the racquet at such an angle before, as and after the ball is hit that topspin is imparted to the ball. This is commonly done by the player practicing topspin shots using balls projected towards the payer by a machine, another payer or a coach.
According to the invention, there is provided a tennis teaching aid comprising a stand, a ball mounted on the stand for rotation about an axis and a guide extending around the ball and defining a racquet angle plane that is parallel to but spaced from a required plane angle of a tennis racquet to hit and rotate the ball with topspin, the majority of the ball being above the guide plane for contact with a tennis racquet in a topspin stroke without the racquet contacting the guide.
In this way, a player can practice hitting the stationary ball, attempting to keep the racquet angle such that the racquet moves parallel to, but spaced from, the guide surface and so that the racquet brushes over the surface of the exposed ball to impart spin to the ball. If the racquet is incorrectly orientated, the racquet will touch the guide surface, so indicating to the player that the stroke has been incorrectly executed. If the racquet is too close to the guide surface or slides over the guide surface, the edge of the racquet will strike the ball at or below the axis of the ball and no or little spin will be imparted. Having the majority of the ball above the plane of the guide surface allows the player to hit the ball with confidence, knowing that, unless the stroke is very awry, the racquet will not touch the guide surface.
Referring to the Figures, the tennis aid comprises a tennis ball 10, a ball mounting 11 and a guide 12. The tennis ball 10, ball mounting 11 and guide 12 are carried, in a manner described in more detail below, on a stand 30 of conventional type that may allow for adjustment of the height of the guide 12 above the ground.
The guide 12, which may be formed of metal or plastics, includes a thin rectangular member 13 having parallel first and second longer sides 14a, 14b spaced by parallel first and second shorter ends 15a, 15b. The member 13 lies in a single plane and, as described below, is connected to the stand 30 and can be rotated about a horizontal axis parallel to the ends 15a, 15b with the second end 15b closer to the ground than the first end 15a so that the angle of the plane of the guide 12 relative to the ground can be adjusted as required—see FIGS. 1a, 1b and 1c, which show three possible angles. In this way, the member 13 of the guide 12 defines a guide plane.
The longer sides 14a, 14b carry respective lugs 16a, 16b that project to one side of the plane of the member 13 and are formed with respective slots, one of which is seen in FIG. 3 at 17a. These are for connection to the ball mounting 11, as described below.
The ball mounting 11 is Y-shaped with two diverging arms 18a, 18b and a leg 19. As seen in FIGS. 1a, 1b, 1c and 5, the arms 18a, 18b are angled relative to the leg 19. A bar 20 projects from the leg 19 beneath the angled arms 18a, 18b and connects to a spindle 21 that extends normal to the leg and projects to either side of the width of the arms 18a, 18b (see FIGS. 2 and 6). The ends of the spindle 21 are threaded. The free ends of the arms 18a, 18b are formed with respective pegs 23a, 23b that extend into respective diametrically opposed holes 24a, 24b in the tennis ball 10. The ball 10 is thus rotatable on the mounting 11 about a horizontal axis.
The lower end of the leg 19 is a screw fit into the top of the stand 30 (see FIG. 6). Once mounted on the stand, the ends of the spindle 21 are inserted through the slots 17a in the lugs 16a, 16b on the member 13 and fixed by nuts 22a, 22b. In this way, the guide 12 is carried on the ball mounting 11 so that, as seen in FIGS. 1a, 1b, and 1c, the majority of the ball 10 projects above the plane of the guide 12 and can be pivotally adjusted relative to the guide 12 so that the amount by which the majority of the ball 10 projects above the guide 12 can be adjusted, as seen in FIGS. 1a, 1b and 1c. 
In use, the stand 30 (see FIGS. 6 and 7) is erected so that the guide 12 is at a desired height and the angle of the guide 12 adjusted to represent the required racquet angle to hit a top spin stroke. For a normal backhand or forehand stroke, the angle may be between 70° and 85°. The amount by which the majority of the ball 10 projects above the plane of the guide 12 and the angle of orientation of the ball 10 can be adjusted as required by releasing the nuts 22a, 22b and moving the slots 17a along the spindle 21 to alter the projection and/or rotating the guide 12 about spindle 21 to alter the angle. The ability to change the angle of orientation allows a choice between a more aggressive vertical topspin or a shallower shot with less spin. Adjustment of the amount by which the majority of the ball is exposed allows a greater exposure to beginners and a lesser exposure for more experienced players. A person then attempts to hit the ball 10 with a tennis racquet trying to move the racquet in a line across the guide 12 with a racquet angle that is parallel to, but spaced from, the plane of the guide 12 (as shown by the arrow 35 in FIG. 7) while hitting the ball 10. If successful, the racquet will not touch the guide 12 (as seen in FIG. 7) and the ball 10 will spin in the mounting 11 with topspin. If unsuccessful, the racquet will touch the guide 12 and so indicate to the player that the stroke has not been performed correctly. By repetition, the player will learn to hit the ball 10 consistently without hitting the guide 12 and so perfect maintaining the racquet at the correct angle to hit a topspin stroke. This is important because, when a movement is repeated over time, a long-term muscle memory is created for that task, eventually allowing it to be performed without conscious effort. This process decreases the need for attention and creates maximum efficiency within the motor and memory systems.
Of course, particularly with more proficient players, a top spin shot will be hit with the player in motion—both forwards and/or rotationally—but there is still an absolute requirement for a correct racquet angle that can be met using the trainer described above with reference to the drawings.
The aid can be used both for forehand and backhand strokes and may be adapted for other spin shots such as serves and sliced backhand strokes.
It is important that the majority of the ball 10 is above the guide plane to allow a proper contact between the ball 10 and a request and to allow a person using the side to be confident of hitting the ball 10 without touching the guide 12. In practice, a person using the aid will always tend to keep the racquet from touching the guide 12 since the majority of the ball is exposed above the guide 12 and so the guide 12 serves a more psychological function than a structural function. People are usually proficient in judging how to keep a racquet head parallel to an adjacent plane. The guide 12 may extend 30-50 cm (11.8-19.7 inches) above and below the ball giving an overall length of 60 cm (23.6 inches) to 100 cm (39.4 inches).
The guide 12 need not be formed by the rectangular member 13. The member 13 could have any desired shape for example circular or oval. The shape need not be a closed shape. It need not be formed by a thin member 13; it could be formed by a plate or by a shaped member with a planar rim that lies in a single plane. The guide 12 could have a portion remote from the ball that defines a curved path parallel to a desired curved path for a racquet prior to reaching the zone of the ball 10.
In the embodiment described above with reference to the drawings, the mounting of the ball 10 is fixed relative to the guide 12. The two diverging arms 18a, 18b and the leg 19 mounting the ball 10 may, however, be resiliently mounted for movement relative to the guide 12 so that, when the ball is struck, it moves into the plane of the guide 12 against the spring load, with the spring loading subsequently returning mounting and the ball 10 to the starting position shown in the drawings before the next stroke.